If hair and crusts can be loosened easily without causing your horse undue stress or pain then remove those. Use a coarse brush or curry and dispose of the hair, dander and crusts in the trash.

Removing these crusts allows air and sunlight into the affected area, which might reduce microbial growth. Depending on the condition being treated, clipping the hair from an affected area may also be useful.

Wet the affected area, either with a water bucket and clean cloth or paper towel, or with a hose. Lather the affected area well, using your fingers to try to remove as much dirt, loose hair, debris and crusts as possible.

Rinse, repeat. Let the shampoo lather stand for 10 minutes, then rinse well and dry. If your vet has prescribed the use of a topical medication, apply that now.

If you have any doubt about whether you should treat a skin condition without veterinary guidance, call your vet to discuss your concerns.

Consult your vet for a recommendation on shampoos and antiseptics.

Do not continue to treat a skin condition yourself over an extended period of time without consulting your vet. If the problem spreads or worsens, it may be more difficult to resolve later. If no improvement in the situation over 3-7 days, then it is time to involve your vet.

Never use very strong antiseptic products that might damage the skin. These usually do more harm than good. Strong does not equate to effective. In fact, often the opposite.

If you use an antiseptic shampoo, be sure to allow the lathered area to set for 10 minutes. This contact time is required for these products to penetrate the coat and kill microbes, and thus to be effective. Always be sure to rinse shampoo off completely. Residual shampoo can cause or worsen existing skin irritation.

Once all of the loose material has been removed you can monitor the bare areas for spread, or the beginnings of hair re-growth over a period of days.